1. Field of the Invention
The invention relates to an image displaying device and an image displaying system, each of which is of a time-division driving system utilizing, for example, shutter eyeglasses.
2. Description of the Related Art
In recent years, active matrix liquid crystal display (LCD) devices, provided with a thin-film transistor (TFT) for each pixel, have been used commonly for displays of devices such as low-profile televisions, portable terminals, and so forth. In such liquid crystal display devices, in general, an image signal is line-sequentially written to an auxiliary capacitor and a liquid crystal element of each pixel from a top to a bottom of a screen, to drive each of the pixels.
Depending upon an application, some of the liquid crystal display devices perform driving (which may be hereinafter referred to as “time-division driving”), in which one frame period is divided into a plurality of time periods and different images are displayed for the respective divided time periods. Examples of the liquid crystal display device utilizing the time-division driving include a liquid crystal display device utilizing a field-sequential system, a stereoscopic image displaying system which uses so-called “shutter eyeglasses”, and so forth.
The field-sequential system is a driving system for performing color displaying, which is achieved by dividing one frame period into three periods, sequentially writing images corresponding to respective colors of red (R), green (G), and blue (B), and emitting respective color lights of R, G, and B from a backlight in synchronization with the writing of each of the images. In general, the liquid crystal display device spatially divides one pixel into a plurality of sub-pixels of R, G, and B, and thus has a reduced use-efficiency of light. However, the employment of the field-sequential system makes it possible to improve the use-efficiency.
The stereoscopic image displaying system utilizing the shutter eyeglasses divides one frame period into two periods, and alternately displays two images having a parallax between each other, which serve as an image for a left eye and an image for a right eye. Also, the stereoscopic image displaying system uses the shutter eyeglasses, which perform switching over between an opening operation and a closing operation of a left-eye section and a right-eye section, in synchronization with the alternate displaying of those two images. When a viewer sees a displayed image by wearing the shutter eyeglasses, the viewer can recognize the displayed image as a stereoscopic image.
Incidentally, in a typical two-dimensional image displaying device, there may be cases where the number of bits in an input original image and the number of bits that can be represented on a display are different. In order to address such cases, for example, a dithering process is often performed as a process for converting (i.e., reducing or expanding) the number of bits in an image signal. As for the dithering process, various proposals have been currently made, such as those proposed in Japanese Unexamined Patent Application Publication No. 2001-134243, No. 2001-282190, No. 2007-94411, No. 2006-506664 (published Japanese translation of a PCT application), and No. 2006-506665 (published Japanese translation of a PCT application), for example.